Field
Various features relate generally to a package on package (PoP) device, and more specifically to a package on package (PoP) device that includes solder connections between integrated circuit (IC) packages.
Background
FIG. 1 illustrates a device 100 that includes a first package 102 and an interposer 104. The first package 102 includes a first die 120 and a first package substrate 122. The first package substrate 122 includes a plurality of pads 124 and a first pad 126. The first package substrate 122 also includes a first dielectric layer 123. The first package substrate 122 may also include a first solder resist layer 127. The first solder resist layer 127 is located on the first dielectric layer 123. The first solder resist layer 127 may also cover a portion of the first pad 126. The first die 120 is coupled to the first package substrate 122 through a first plurality of solder balls 128. Specifically, the first die 120 is coupled to the first plurality of pads 124 through the first plurality of solder balls 128. A second plurality of solder balls 130 is coupled to the first package substrate 122.
The interposer 104 includes a second pad 146. The interposer 104 may be a package substrate of a second package (not shown). The interposer 104 also includes a second dielectric layer 143. The interposer 104 may also include a second solder resist layer 147. The second solder resist layer 147 is located on the second dielectric layer 143. The second solder resist layer 147 may also cover a portion of the second pad 146. The interposer 104 is coupled to the first package 102 through a first solder ball 156. For example, the first solder ball 156 is coupled to the first pad 126 of the first package substrate 122, and the second pad 146 of the interposer 104. The solder ball 156 is located in a cavity of an encapsulation layer 150 of the first package 102. The cavity of the encapsulation layer 150 in which the solder ball 156 is located in is formed by using a laser process (e.g., laser ablation).
As shown in FIG. 1, the first pad 126 has a surface that is in contact with the solder ball 156. The surface of the first pad 126 that is in contact with the solder ball 156 has a relatively rough surface roughness. This is due to the fact that a laser is used to remove the encapsulation layer 150 over the first pad 126. The result of this laser process (e.g., laser ablation) is an uneven surface (e.g., rough surface) on the first pad 126. An uneven surface or rough surface on the first pad 126 can result in a weak joint, a poor joint and/or an open joint between the first pad 126 and the solder ball 156. A weak joint or poor joint connection can result in poor and/or unreliable signal quality in the device 100, which can cause poor performance in the device 100.
Therefore, there is a need for a device (e.g., package on package (PoP) device) with strong and reliable joints to ensure better quality and/or performance signals between packages. Ideally, such a device will have a better form factor, be cheaper to fabricate, while at the same time meeting the needs and/or requirements of mobile and/or wearable devices.